Fibers made of polyglycolic acid have been used as fibers having biodegradability and bioabsorbability in various fields such as the medical field, and have been conventionally produced by spin-drawn yarn method (SDY method). In the SDY method, however, the drawing is conducted after spinning without winding. Hence, if yarn break or the like occurs during the drawing, a large amount of resin is discharged in the spinning step. Accordingly, the SDY method is inefficient for mass-production, and it is not easy to reduce the production costs of polyglycolic acid fibers. For this reason, the applications of polyglycolic acid fibers are limited to those in special and high value added fields, such as surgical sutures.
On the other hand, polyolefin fibers, nylon fibers, polylactic acid fibers, and the like are produced in such a manner that undrawn yarns after spinning are once wound or put in cans to be kept, and then drawn (see, for example, Japanese Unexamined Patent Application Publication No. 2005-350829 (PTL 1), Japanese Unexamined Patent Application Publication No. 2006-22445 (PTL 2), Japanese Unexamined Patent Application Publication No. 2007-70750 (PTL 3), Japanese Unexamined Patent Application Publication No. 2008-174898 (PTL 4), and Japanese Unexamined Patent Application Publication No. 2005-307427 (PTL 5)). In this method, the spun undrawn yarns can be drawn in a bundle, and the spinning step and the drawing step are each independently conducted, because it is unnecessary to draw yarns immediately after the spinning. Hence, this method achieves a high productivity, and is suitable for mass-production.
However, production of a polyglycolic acid fiber by this method involves a problem that undrawn yarns of polyglycolic acid wound or put in cans agglutinate during the keeping, and the undrawn yarns are difficult to release, so that the undrawn yarns cannot be drawn.